This application relates to liquid crystal polycarbonates and to methods of preparing such materials.
Liquid crystalline materials are materials that in a liquid state display anisotropic, i.e., ordered, molecular arrangements. In the case of polymeric materials, the liquid state is generally a melt in which the polymers are aligned, although some lyotropic polymers in which the alignment occurs in solution are known. Most commercial applications of liquid crystal polymers are based on polyesters or polyamides (for example Kevlar®).
U.S. Pat. No. 4,831,105 describes liquid crystalline polycarbonates made by melt transesterification of diphenylcarbonate (DPC) and a mixture of methylhydroquinone and 4,4′-dihydroxybiphenyl. U.S. Pat. No. 5,102,975 describes liquid crystal polycarbonates made by a melt transesterification of DPC and a mixture of 4,4′-dihydroxybiphenyl and 4,4′-dihydroxyphenylether. These liquid crystal polycarbonates have desirable properties for use as molding compositions because of high heat resistance, outstanding dimensional stability and excellent solvent resistance. However, the difficult manufacturing processes for these materials have prevented substantial commercial development. There is therefore a need for an improved and more facile method to make liquid crystalline polycarbonates. This application provides such a method, and further provides compositions made by this method.